Multispeed supercharger



June l1, 1940. E. F. lPufecrs. 2,293,343

T MULTISPEED SUPERCHARGER Filed June 5, 1938 atented June 11, 1940 UNITED STATES PATENT OFFICE of New York Wright Aeronautical Corporation, a corporation Application June 3, 1938, Serial No. 211,494

6 Claims. (Cl. E30-131) This invention relates to variable capacity blowers, and is particularly useful as applied to aircraft engine superchargers.

In the aircraft engine art, multispeed superchargers have become necessary to provide maximum power outputs at high altitudes, and the multispeed organization ordinarily comprises a selective step gearing by which the supercharger impeller may be driven at various ratios with respect to engine crankshaft speed. This step gearing involves considerable complication, and one of the objects of this invention is to provide a multispeed supercharger which avoids the necessity of change speed gearing.

A further object of the invention is to provide a variable speed blower or supercharger incorporating impeller-s of different diameters adapted to be selectively driven at uniform speed. When the large diameter impeller is in operation, the greater peripheral speed thereof affords a supercharger boost greater than that which the small diameter impeller can supply by itself. When low boost is required, the large diameter impeller may be drivably disconnected so it can idle freely, wherefore 25 it does not interfere with the boost causedby the small impeller but, of itself, does no work upon the air or other fluid which is being worked upon.

Other objects and advantages will be apparent from a reading of the annexed specification and 20 claims, together with an examination of the accompanying drawing, in which:

Fig. l is a longitudinal section through avariable capacity supercharger according to the invention, and

Fig. 2 is a fragmentary end elevation of the su" percharger impellers taken `on the line 2--2 of Fig. l.

For purposes of illustrating the invention, I have chosen to show it in an environment approl0 priate to an airplane engine supercharger. In Fig.

1, Ill and I I, respectively, represent housing members within which the supercharger is carried, said members normally forming a part of an engine crankcase system. .The members In and II are provided with bearings I2 and I3, respectively, within which a plurality of coaxial shafts are journaled, i4 representing a supercharger drive shaft carrying a supercharger drive gear I5 at its right hand end. To the shaft I4 is splined a primary supercharger impeller I6 as at I'I, the shaft continuing through the housing II and terminating in a piston element I8. Embracing, and journaled on the shaft I4 is a secondary hollow shaft I9 carrying, at its right hand end, a secondary supercharger impeller 20, and at its left hand end a cylinder 2| within which the piston l is slldably engageable. Slight axial freedom of the shaft I9 is permitted for a purpose hereinafter to be disclosed.'

The primary impeller I6 is of conventional form comprising a back plate 24 on which are formed integral radial impeller vanes 25 open at their inner ends to an intake duct 26 and discharging substantially radially at their outer ends. A friction plate 28 is formed on the back side of the impeller. The secondary impeller comprises a central web 29 carrying, at its outer periphery, an annular belt of impeller blades'30,

the inner edges of which clear the outer ends of the blades as at 3|. The outer ends of the blades 30 run close to the vanes 32 of a conventional diffuser plate 33 carried by the housing ele ment I0. A friction disc 34 is xed toward theE inner part of the member 29' so as te frictionally coaet with the plate 28.

A uid pressure line, from an engine oil pump or the like, connects to the housing Ii at 36, and by suitable drillings 31 and an annular recess 38 in the shaft I9, this pressure fluid may be ad mitted to the cylinder 2|, selectively. When pressure fluid is admitted to the cylinder 2 I, the cylinder is moved toward the right with respect to the piston I8, thus engaging the friction faces 28 and 34 and effecting a unitary drive between the impellers I6 and 20. When pressure is cut off from the cylinder 2 I, fluid leakage will quickly relieve the frictional engagement permitting the secondary impeller 20 to idle rotationally while the primary impeller I6 continues to be driven from the power source. The connection communicates through a shut-off valve 40 and a pressure pump 4I, shown diagrammatically.

The location of the clutch is favorable for adequate cooling during slipping engagement, since heat will dissipate into the impeller wheels which normally run very cool due to the passage of large volumes of air over their, and their vane, surfaces.

The first stage of supercharging results from rotation of the primary impeller I6, while the secl ondary impeller 20 idles rotationally; in virtue of the small diameter of the primary impeller I6,

the tip speed of its blades 25 is moderate. When the secondary impeller 20 is clutched for unitary rotation with the primary impeller, the two impellers in eiect become a single impeller of large diameter whose tip speed, and thus available supercharge, is much greater than that afforded by the primary impeller alone, with, however, no change in the speed of rotation.

According to well known principles of super- 'charger design, the amount of supercharging in either stage will be determined by the impeller diameters and by the gear ratio between the impellers and the driving shaft.

'Ihe friction. clutch and hydraulic shift therefor is a simple. and direct arrangement for selectively driving the large diameter impeller with the small diameter impeller, but obviously, other means may be used for providing driving eiort for the secondary impeller.

While I have described my invention in detail in its present preferred embodiment, it 'will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modications and changes.

I claim as my invention: l

1'. A variable capacity blower comprising a rst impeller having blades, means to rotate said impeller at a iinite speed thereby producing an impeller blade speed proportional to its diameter; means to boost the output of said iirst impeller comprising a second impeller having blades, em bracing and of larger diameter than the first impeller and selectively operable means to selectively drive said second impeller at unitary speed with the first or to leave it rotationally free, said boost being aiorded by the greater tip speed of the second impeller due to its larger diameter,

. and a stationary ring of diffuser vanes embracing fluid, a second impeller coaxial with the first,

having substantially radial blades together embracing the blades of the first impeller and having an outer diameter substantially greater than the diameter of the blades of the rst impeller, and means selectively operable to clutch said second impeller for unitary rotation with said first impeller todo additional work upon the fluid issuing from the flrst impeller or to declutch said second impeller for idling, and a stationary diffuser embracing said secondary impeller into which the impellers discharge.

3. In a supercharger, in combination, a primary rotatable impeller, a second annular rotating impeller embracing the first and selectively clutchable thereto,.means selectively operable to clutch the second impeller to therst and to free the second impeller for idle rotation, and a stationary diffuser embracing both impellers.

4. In a supercharger, in combination, a pair of Y coaxial impellers having radially disposed blades,

the blades of one impeller deflning an annulus embracing the bladesV of the other impeller, and means selectively operable to leave the annular impeller rotationally free o'r to clutch same for unitary rotation with the other impeller, said selectively operable means comprising friction facings on respective impellers and mechanism to bodily move one of the impellers to effect frictional driving engagement between said impellers.

5. In a supercharger, in combination, a pair of coaxial impellers having radially disposed blades, the blades of one impeller defining an annulus embracing the blades of the other impeller, and means selectively operable to leave the annular impeller rotationally free or to clutch same for unitary rotation with the other impeller, said selectively operable means comprising friction facings on respective impellers and hydraulic mechanism to bodily move one of the impellers to eiect frictional engagement of said facings.

6. In a supercharger, in combination, a driven primary rotating impeller, "a second annular rotatable impeller, means selectively operable to clutch the impellers to one another for unitary rotation and for releasing the second impeller for idle rotation, and a stationary diffuser embracing both impellers into which the yprimary or both impellersdischarge.

EROLD F. PIERCE 

